This application is related to Japanese application No. HEI 11 (1999)-223463 filed on Aug. 6, 1999, whose priority is claimed under 35 USC xc2xa7119, the disclosure of which is incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a semiconductor device comprising a semiconductor element connectively mounted on a flexible substrate. More particularly, it relates to a chip-on-film (hereinafter referred to as COF) structure and a tape carrier package (hereinafter referred to as TCP).
2. Description of Related Art
In a TCP, as shown in FIG. 9, an aperture (device hole) is provided in advance through a base film 21 of an insulating film (tape) in a region for mounting a semiconductor element. A patterned wiring 22 is formed on the base film 21 with the intervention of an adhesive layer 28 and extends toward the aperture, at which an edge 24 of the patterned wiring is connected to a semiconductor element 23. The base film of the TCP is customarily a polyimide film of 50 or 75 xcexcm thick. The polyimide film of such thickness is sufficient in mechanical strength. Therefore the film is wound on a reel using sprocket holes formed in the outer sides of the TCP and conveyed on reel-to-reel in an assembly line.
Different from the TCP, a base film 21 of a COF does not form an aperture for mounting a semiconductor device 23 as shown in FIGS. 10(a), 10(b) and 11. Briefly, the semiconductor element 23 is connectively mounted on the surface of the base film 21. In view of applications of the COF, a flexible thin insulating tape is used as the base film, on which a patterned wiring is arranged and electrically connected to a corresponding terminal of the semiconductor element. A connector for externally connecting the patterned wiring is connected to a liquid crystal display, a printed substrate and the like. A solder resist is applied for ensuring insulation on an exposed portion of the patterned wiring other than the wiring connected as mentioned above.
The COF utilizes, as the base material, a polyimide film of 20, 25 or 40 xcexcm thick cut in a sheet form. When it is conveyed on reel-to-reel similarly to the TCP, in particular when the COF of not more than 25 xcexcm thick is to be fabricated, a reinforcement member of a thick film is adhered as a reinforcement tape for conveying the TCP. The reinforcement member is removed by stamping the base material with a mold to separate each user-utilizing area, and is not used anymore as the reinforcement member after the TCP is conveyed.
FIG. 9 is a sectional view illustrating the conventional TCP, FIG. 10(a) is a plan view observed from a semiconductor element-mounted surface of the conventional COF, FIG. 10(b) is a plan view observed from a surface opposite to the semiconductor element-mounted surface and FIG. 11 is a sectional view illustrating a structure of the conventional COF. In FIGS. 9 to 11, reference numeral 21 denotes the base film, 22 the patterned wiring, 23 the semiconductor element, 24 a portion of the patterned wiring connected with the semiconductor element, 25 a connector for externally connecting the patterned wiring, 26 a bump, 27 a resin, and 33 an outer shape into which the semiconductor device is stamped.
The above-mentioned COF has the drawback that the base material is thin and elastic so that width of an outer lead row and that of an inner lead row (total pitch) are imprecisely sized. Also, the reinforcement member is adhered after stamping the semiconductor element, which increases the production costs and the reinforcement member may not be positioned at the right position. The base material does not bend at a fixed position when mounting it on a liquid crystal panel, therefore it is difficult to incorporate the mounting step into the assembly line. Further, warpage of the film occurs in a reflow process performed after the components are mounted.
Now, the COF is expected to satisfy a demand of multiplying the number of pins. In order to satisfy this demand as well as another demand of device miniaturization, the connectors for externally connecting the patterned wirings and the portions of the patterned wirings connected with the semiconductor element need to be arranged with fine pitches therebetween. There are several problems to be solved to make the fine pitches, one of which is that the above-mentioned total pitch should be sized with great precision. A thin insulating tape having high elasticity has been used to meet a demand of flexibility and the reduction in thickness. However, the thin insulating tape is poor in mechanical strength and may be excessively expanded or contracted. In particular, the base material used for the COF is highly absorbent and less stable as compared to the base material used for the TCP, for which the above-mentioned fine pitches are difficult to obtain.
The TCP requires the base material of about 20 to 25 xcexcm thick because a low temperature treatment needs to be performed to mount the TCP on a plastic liquid crystal panel. Thus, the TCP also suffers from drawbacks similar to those of the COF.
A semiconductor device of the present invention is a semiconductor device in which a patterned wiring including a connector for external connection is formed on an elongate base film, a semiconductor element or the semiconductor element and a component other than the semiconductor element are mounted on and electrically connected with a portion for connection of the patterned wiring, an elongate reinforcement member is provided on a surface of the base film opposite to a surface on which the patterned wiring is formed, the reinforcement member having sprocket holes at positions corresponding to the lengthwise sides of the base film, characterized in that the reinforcement member is further provided on said opposite base film surface in a region corresponding with a region on which the connector for external connection is formed.
In the semiconductor device according to the present invention, it is desirable that the reinforcement member is provided directly or with the intervention of an adhesive layer on the opposite base film surface in the region corresponding with the region on which the connector for external connection is formed.
Desirably, the reinforcement member is provided on the base film with the intervention of the adhesive layer so that the reinforcement member can be exfoliated (or peeled) at the adhesive layer.
Also desirably, the reinforcement member is provided on the opposite base film surface such that the reinforcement member can be exfoliated from the base film at an interface therebetween.
Further preferably, the reinforcement member is further provided on the opposite base film surface in a region corresponding with a region on which the semiconductor element or the semiconductor element and the component other than the semiconductor elements are mounted.
The thickness of the reinforcement member is desirably 15 xcexcm or more to 400 xcexcm or less.
Also desirably, the reinforcement member comprises an organic film.
A process for manufacturing a stamped semiconductor device according to the present invention is characterized in that the base film constituting a semiconductor device (unstamped semiconductor device) described in the preceding paragraphs is separated by using an outer shape stamping to have a predetermined shape, thereby to cut out a region of the reinforcement member including the sprocket holes and leave the reinforcement member on said opposite base film surface only in a region corresponding with the region on which the connector for external connection is formed, only in a region corresponding with the regions on which the connector for external connection is formed and the semiconductor element is formed, or only in a region corresponding with the regions on which the connector for external connection is formed, the semiconductor element is mounted and the component other than the semiconductor element is mounted.
A liquid crystal module according to the present invention is characterized in that the unstamped semiconductor device is stamped to have a predetermined shape and mounted on a liquid crystal panel.
A process for mounting the liquid crystal module according to the present invention is characterized by stamping the unstamped semiconductor device to have a predetermined shape and mounting it on the liquid crystal panel to fabricate a liquid crystal module, exfoliating the reinforcement member located at least on a bend portion of the base film, and mounting the liquid crystal module on a desired electric product.
Further, a process for mounting a liquid crystal module according to the present invention is characterized by removing all the reinforcement member provided on the base film in the above-mentioned liquid crystal module and mounting the liquid crystal module on a desired electric product.
These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.